The nation's response to the needs for energy self-sufficiency could increase the number of hazardous agents released daily into the environment. Efficient and economical systems are needed to predict the susceptibility of humans to hazardous agents and to monitor human populations for adverse genetic effects that may be caused by unforeseen mutagens. Most likely, further development of unscheduled DNA synthesis, a form of DNA repair synthesis, will assist in meeting these needs. The significance of unscheduled DNA synthesis will be enhanced by correlations of the extent of DNA repair with measurements of cytogenetic aberrations and with mutagenesis in mammalian cells. BIBLIOGRAPHIC REFERENCES: A.D. Mitchell, D.E. Robinson, D.T. Tajiri, T.-J. A. Kan, G.P. Sterling, P.A. McAfee, and C.F. Kirchner. The Relationship of unscheduled DNA Synthesis to Mutagenesis and Chromosomal Aberrations. Mutation Res.; in press, 1977 (abstract). A.D. Mitchell. The Potential Utility of DNA Repair for Predicting the Effects of Human Exposure to Hazardous Agents. Environ. Health Persp.; accepted for publication, 1977.